Shock absorbing strut



July 20, 41937. c. v. JOHNSON SHOCK ABsoRBING STRUT Filed Jan. 21, 1935IN VEN TOR. C RL l/ Jo/ws o/v BY Ql/b. ica/(M v A TTORNEY Patented July"2o, 1937 UNITED STATES 2,os7,379. snocx ABsoaBING sraUir Carl V.Johnson, South Bend, Ind., assgnor to Bendix Aviation Corporation, SouthBend, Ind., a corporation of Delaware y Application January 21,` 1933,Serial No. 652,915 8 Claims. (Cl. 267-64) 'Ihis invention relates toshock absorbers and more particularly to shock absorbing struts foraeroplanes.

It has been found that shock absorbing struts of the hydraulic pneumatictype for aircraft and other types of shock absorbing struts aresubjected to considerable bending stress, due to side loads, which has amaximum at or near the end of the packing chamber receiving the packing10 nut.

It has also been found that in shock absorbing struts for aircraft usingdiaphragms having metering orifices, the struts occasionally developweakness where the diaphragm is installed.

- 'I'he present invention aims to overcome these objections by employinghighly desirable structure tending to materially strengthen the strutsat both the packing chamber and diaphragm.

An object of the invention is to provide a shock absorbing strut foraeroplanes including telescopic members and means for effectivelysecuring the members together so that the strut may be materiallystrengthened at the joint.

Another object of the invention is to provide a shock absorbing strutfor aeroplanes including telescopic members wherein spaced bearingmembers are secured to one member on either side of a packing gland toassure a bearing of some length between the members and render themresistant to bending stresses.

Another object is to provide, in a shock absorbing s trut includingtelescopic members wherein the smaller member carriesv a bearing pistonand the larger carries a bearing collar,

means for limiting the minimum spacing between said bearlng piston andcollar to assure strength against bending in all telescopic positions.

A further object of the invention is to provide a shock absorbing strutincluding a cylin- .der having a packing chamber, a piston rod in thechamber having a head positioned for reciprocation in the cylinder, anda sleeve member supported adjacent the inner end of the chamber whichmay be adapted to guide the piston rod and limit its outward movement.

A further object is to provide in a shock absorber comprising a pair voftelescopic members, properly spaced bearing means .assuring at all timessuilcient overlap between the members to prevent bending.

Another object of the invention is to provide a shock absorbing strutfor aeroplanes including telescopic cylindrical sections joinedtogether,

` a diaphragm secured therein at the joint, and a snubbing tube andorice plate supported on the diaphragm and removable as a single unit.

Another object of the invention is to provide a shock absorbing strutincluding a cylinder having a packing chamber and means reinforcing 5the packing chamber.

A further object of the invention is to provid a shock absorbing strut-including a cylinder having a packing chamber, a piston rod in thechamber having a head positioned for reciprocation 10 in the cylinder,and a member supported in the Chamberland arranged inthe cylinder forlimiting the movement of the piston head.

A feature of the invention is telescopic cylinder sections, one of whichis provided with an l5 irregular prole providing greater area forwelding the sections together.

Another feature of the inventionis an orifice plate and snubber cylinderremovable as a single unit.

Another feature of the invention is a packing chamber and a packing nutthreaded therein having an unthreaded part piloted into the cha ber.

Another feature of the invention is a packing 25 ring and sleevearranged in a. cylinder to limit movement of a. piston positioned forreciprocation in the cylinder. v

A further feature of the invention is a cylinder having a packingchamber sleeved thereon 30 and provided with means for impartingrigidity thereto.

Other objects'and features of the invention will more fully appear fromthe following description taken in connection with the draw- 35 lng, andin which:

Figure 1 is a vertical sectional view of a shock absorbing strutembodying the invention;

Figure 2 is a fragmentary view illustrating the joint between thetelescopic sections of the cyl- 40 inder;

Figure 3 is a cross-sectional view substantially on line 3--3, Figure 1;

Figure 4 is a vertlcalsectional view, partly broken away, illustrating amodification; and 45 t Figure 5 is a side elevation ofv the modifica-Referring to the drawing and more specic details of the invention, I0represents a section of a cylinderl closed at one end by a cap vl2having 50 formed thereon a clevis I4 for attaching the fuselage of anlaeroplane. 'Ihe other end of the cylilider section has secured theretoa diaphragm- As shown, the diaphragm has a double diam- 55 eterproviding a shoulder I8 for the reception of the end of the cylindersection to which the diaphragm is secured. The diaphragm also has adouble diametral bore 20. A case-hardened plate 22 having a meteringvorifice 24 is fitted in the bore havingl the larger diameter and isretained against displacement by screws 26.

Positioned concentrically Within the cylinder section I is a snubbingcylinder 28 having upon one end a circumferential flange 30 clampedbetween the t diaphragm and the caseehardened plate having the meteringorifices. By removing the screws 26 the plate having the meteringorifices and the snubbing cylinder may be easily removed as one unit.The other end of the snubbing cylinder 28 is provided with a iiap valve32, the purpose of which will hereinafter appear, and a plurality ofopenings 34 are in the wall 0f the snubbing cylinder adjacent thediaphragm.

As shown, the cylinder section I0 has suitably secured in the wallthereof, adjacent the cap I2, a short sleeve 36 internally threaded forthe reception of a valve 38 through which suitable hydraulic fluid andair or gas may be admitted to the cylinder under pressure.

-One end of a section of a cylinder 40 telescopes the end of thecylinder section I0 supporting the diaphragm I6. To lend strength andrigidity to the structure, so that the strut may withstand all stressesand strains imposed thereon due to side loads, also to preventdistortion due to welding the cylinder sections I0 and 40 together, thetelescoping end of the cylinder section 40 extends beyond the diaphragmI6 and is notched as indicated at 42, so that in welding the partstogether the surface over which the piston moves is not affected andadditional welding surface may be obtained by reason of the increasedperimeter due to the notches.

The other end of the cylinder section 40 has a packing chamber 44 havinga shoulder 46 in its inner end on which is seated a packing retainingring 48 having a sleeve 5D extending into the cylinder section, whichsleeve may be separate from the ring 48 if desired, and the other end ofthe packing chamber is internally threaded to receive a packing nut 52,suitable packing glands 54 being interposed between the packingretaining ring 50 and the packing nut 52, and suitably secured on thewall of the packing chamber are brackets 56 for suitable bracing, notshown.

A hollow piston rod 58 is positioned for reciprocation with the packingchamber. This rod has secured on one end thereof a sleeve or collar 60for the reception of the axle of the aeroplane and connecting the sleeveto the piston rod are braces 62 which may be spot welded or otherwisesecured to these parts. The other end of the piston rod has suitablysecured thereto a head `or piston 64 supporting 'a metering pin 68 forco-l piston tube is subjected to considerable bending` stress which ismaximum at or near the outer end of the packing chamber. Accordingly, byincreasing the space between the head of the piston and the packing` nut52, by employing piloting the sleeve 50, thebearing conditions fortransmitting side loads are greatly improved. II desired, the sleeve 50may have a close sliding yfit with the piston tube 58, wherebyadditional rigidity may be gained or the close it of piston head 64 withthe cylinder 40 and the necessary finished internal cylinder surface maybe eliminated.

The piston head 64 has a series of ducts 6B drilled diagonally throughthe head to provide .for free access of fluid from the cylinder sectioninto the annular chamber around the piston rod created as the pistonmoves along the cylinder on the compression stroke, thus keeping thepacking glands under pressure at all times.

A modification of the invention is illustrated in Figures 4 and 5. Inthis modification the packing chamber 44 is formed by a short tubularsection sleeved on the cylinder section 40. As shown, the short tubularsection has a notched or irregular profile 12 on its telescopic end, 'sothat greater surface may be had for welding the short tubular section tothe cylinder section. This structure materially strengthens the strut atthe packing chamber Where the maximum strains are imposed due to sideload.

Assuming that the strut is filled .with suitable hydraulic liquid andair or gas under pressure, it will under impact of landing cause thehydraulic liquid to be forced through the metering orifice in thediaphragm, past the metering pin, into the upper cylinder section wherethe air or gas will be compressed by the rise of the liquid, and thiscombined resistance oiered by the compression of the air or gas and theflow of liquid produces the work curve desired.

On the compression stroke fluid ows through the ducts 68 in the pistonhead into the annular chamber. formed -back of the piston head andmaintains the packing glands under pressure. The liquid passes freelythrough the iiap valve on the top of the inner chamber into which themetering pin extends. and'on the returnV stroke the iiapl valve closesdue to the pressure of the compressed air or gas forcing the liquid toreturn through the smaller opening in the base of the snubber chamber,thus snubbing the rebound that would otherwise result.

Although this invention has been described in connection with certainspecic embodiments,

the principles involved are susceptible of numerous other applicationsthat would readily occur to persons skilled in the art. 'I'he inventionis, therefore, to be limited only as indicated by the scope of theappended claims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is:

1. A shock absorbing strut comprising telescopic cylinder sectionsoverlapped and secured together, a diaphragm secured therein and restingagainst the peripheral end'of the inner cylinder, and the walls of theouter cylinder section, said outer cylinder section extending past thediaphragm and provided with securing notches through the wall thereof.

2. A shock absorbing strut comprising telescopic sections lapped andjoined together, a diaphragm-secured therein at the joint and seated onthe end of the inner cylinder, and a removable oriflce plate supportedon .the diaphragm, said diaphragm resting against the inner wall of theouter telescopic section.

3. A shock absorbing strutl comprising telescopic cylinder sectionsjoined together, a diaphragm secured therein at the joint, an oriceplate supported by the diaphragm, and a snubber cylinder clamped betweenthe diaphragm and the orice plate.

4. A shock absorbing strut comprising telescopic cylinder sectionssecured together, an

apertured diaphragm secured therein at the joint, a plate supported bythe diaphragm having an orifice' registering with the aperture in thediaphragm, and a snubber cylinder arranged concentrically in o ne of thecylinder sections and provided with a flange clamped between the orlceplate and the diaphragm.

5. A shock absorbing strut comprising telescopic cylinder sectionsoverlapped and secured together, an apertured diaphragm secured thereinand resting against the peripheral end of the inner cylinder, a pistonreciprocating in the outer cylinder and adapted to move toward said dia-20 phragm and said peripheral end, said cylinders being secured togetherat a point beyond the portion of the cylinder sections subjected topiston travel.

6. In a shock absorbing strut. a pair of telescopic cylinders securedtogether in overlapping arrangement, and a diaphragm in the outercylinder and secured against endwise movement by abutment against thesmaller cylinder and sldewise movement by direct engagement with theside walls of the outer cylinder. v

7. In a shock absorbing strut, an inner cylin drical member, and outercylindrical member having an irregular profiled end telescoped over saidinner cylinder and Welded thereto, a piston in the outer cylinder and adiaphragm within the outer cylinder and resting against the end of theinner cylinder whereby the cylinder portion not exposed to Weldingtemperatures is employed for reciprocation of the piston.

8. A shock absorbing strut comprising telescopic cylinders joinedtogether, a diaphragm secured at the joint and bearing against the endof the inner cylinder and the side walls of the outer cylinder, saiddiaphragm including an orice plate arranged on a shouldered seat formedin similar relation to the shoulder formed by the end of the innertelescopic cylinder.

CARL V. JOHNSON.

